It is standard practice to protect the water or steam-carrying boiler tubes in a commercial furnace with refractory materials. In many cases such boiler tubing is disposed in closely spaced arrays, and these arrays can be protected with a substantially monolithic wall of refractory tile.
Bailey, U.S. Pat. No. 1,719,642, discloses tile for use in such an array of closely spaced tubing Metal-backed, ceramic-faced tiles are hung from bolts anchored between the tubes. The tubing array is covered with a substantially monolithic wall of tile completely encircling the tubing.
Lawson, U.S. Pat. No. 3,797,416, describes boiler tube protection for powdered coal-fired boilers. A substantially monolithic protective wall with tongue and groove connections between the protective parts completely encircles the tubing.
Graham, et al., U.S. Pat. No. 3,828,735, discloses a substantially monolithic wall of tile to protect a closely-spaced boiler tube array. The tiles are hung from T-shaped anchors between the tubes.
Fournier, et al., U.S. Pat. No. 4,809,645, discloses a closely-spaced boiler tube array covered with a substantially monolithic wall of individual refractory tiles held against the tubing by means of fins projecting from the tubing.
Aiken, et al., U.S. Pat. No. 5,243,801, describes a substantially monolithic refractory tile wall to be hung on a closely-spaced array of boiler tubing by means of T-shaped anchors affixed between the tubes.
Whereas closely spaced boiler tubes in a furnace can be protected economically with a substantially monolithic wall of refractory tile, when the boiler tubes are spaced a greater distance apart it may not be economically feasible to provide a complete wall of protection. Rather, it may be more desirable to protect each water tube individually. This situation arises in several different contexts.
For example, Guskea, U.S. Pat. No. 3,914,100, describes protective ceramic tile for spaced apart water tubes in a steel mill reheat furnace. A pair of hollowed ceramic tiles interlock along their longitudinal edges to completely encircle the tubing.
Also, Errington, U.S. Pat. No. 4,071,311, discloses refractory sheathing for horizontal water pipes in a steel mill reheat furnace; the sheathing consists of two layers which completely surround the tubing, a fibrous layer overlaid with refractory tile.
Finally, Green, et al., U.S. Pat. No. 4,682,568, describes ceramic tile for protecting individual spaced superheater tubes. The shielding includes two interlocking semicylindrical refractory shapes which completely encircle the steam tube. The interlock between the halves of the tile requires that they be slid together about the tube by relative motion parallel to the tubing and, thus, that the tubing be accessible from all sides for initial installation or replacement. These conditions cannot always be met. To replace a single cracked or otherwise damaged tile, many of the tile on the tube must be removed to slide the damaged piece off.